The subject matter disclosed herein relates generally to hot water heaters, and in one embodiment to a hot water heater configured with a proportional-integral-derivative (PID) control to vary the temperature of a fluid in the hot water heater.
Hot waters heaters are typically configured with limited control as to the temperature of the fluid (e.g., water) disposed therein. High and low threshold temperatures are often used to maintain the temperature of the fluid. Fluid temperature at or below the low threshold temperature will activate a heating device. Likewise temperatures at or above the high threshold temperature will deactivate the heating device.
Hot water heaters of this configuration are susceptible to peak demand, which can drain fluids at hotter temperature (e.g., hot water) from the water heater at a rapid rate. This rate often exceeds the rate of heating of the fluid. Thus the temperature of the fluid can remain near the lower threshold value until the end of the period of peak demand.
Moreover, because the control structure is effectively limited to the high and low threshold values, hot water heaters of this configuration expend a great deal of energy. Outside of the period of peak demand, fluid that is left in the hot water heater for extended periods of time will cool. This cooling will eventually activate the heating device, which is thereafter left active until the fluid reaches the high threshold temperature. Such cycling will occur variously over the course of time, during which little if any need or usage of the fluid will occur despite the expenditure of energy that is required to heat the fluid.
Therefore it would be advantageous to have a hot water heater that can maintain the temperature of the fluid, while also reducing the energy necessary to heat the fluid.